A man has been charged with the manslaughter of Constable William "Bill" Crews, who was shot during a police raid at a Bankstown unit last year.

Philip Nguyen, 55, was charged when he appeared in Burwood Local Court this morning.

Constable Crews, 26, was a detective-in-training when he was struck by a bullet in a shoot-out during a night-time drug raid at the unit on Cairds Avenue on September 8.

He later died in Liverpool Hospital.

In the days after his death, police believed Constable Crews was accidentally killed when he was hit by a bullet from a colleague's gun.

The charge follows an investigation by a critical incident team.

Constable Crews was posthumously promoted to the rank of detective constable by NSW Police Commissioner Andrew Scipione at his funeral.

Mr Scipione also gave Constable Crews the Commissioner's Valour Award, the force's highest honour, for the bravery displayed during the raid.

He was already on his way to joining the elite ranks of the state crime command only three years after graduating from Goulburn Police College, Mr Scipione said at the time.

"William was not in the NSW Police Force for long but, by anyone's record, he was on a rapid upward path," Mr Scipione said.

"It is a place where our most-skilled detectives want to go. If you get there at all, it's usually after a long apprenticeship. If you get there quickly, it is because you have something that sets you apart. And William had that certain something."

Mr Nguyen, who did not apply for bail, will appear again in Burwood Local Court on July 6.

- with Nick Ralston